Personalized medicine is transforming modern healthcare by recognizing that each patient’s biology, environment, and lifestyle influence treatment outcomes. This approach is especially critical for pediatric and geriatric populations, where physiological variability, comorbidities, and age-specific responses demand highly tailored therapeutic strategies.This new volume provides a comprehensive and timely exploration of advances in individualized treatment for these vulnerable groups. The volume examines a wide range of conditions—including cancer, respiratory and gastrointestinal diseases, endocrine and neurological disorders, infections, and vaccination strategies—highlighting how therapies can be adapted to meet the distinct needs of both children and older adults. Emphasis is placed on understanding age-related physiological differences and their impact on drug efficacy and safety.The book also addresses key enabling technologies and methodologies shaping this field, including biomarkers, pharmacokinetics and pharmacodynamics, wearable health technologies, and precision medicine frameworks. In addition, it explores the growing role of artificial intelligence and machine learning in improving diagnostic accuracy, optimizing treatment pathways, and expanding access to personalized care.Bridging clinical practice and emerging research, this volume offers valuable insights into improving healthcare outcomes through targeted and adaptive treatment strategies. It serves as an essential resource for healthcare professionals, researchers, policymakers, and students seeking to advance patient-centered care across the lifespan.